1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming system.
2. Description of Related Art
Sheet processing apparatuses that perform trimming to cut off a part of a sheet, such as fore edge trimming to trim the fore edge of a saddle-stitched booklet, have been known in the art.
Typically, an apparatus for trimming includes a container to collect chips produced in the trimming process and is configured such that a detector detects whether the top of chips piled up in a mountain shape in the container has reached a predetermined height. For example, when the detector detects that the top of the piled chips has reached the full level of the container, it is notified to a user so that he/she can take out the container from the apparatus to dispose the chips.
In such apparatuses, it is desirable that chips are collected in a container with leaving as little space as possible in order to reduce a burden on the user of disposing the chips. For this reason, a proposal has been made in which a container moves back and forth so as to flatten the piled chips in the container (e.g. see JP 2014-043328A).
However, a problem with the technique of JP 2014-043328A is that when a chip sticks to a detecting area of the detector, for example, due to reasons that the chip is electrostatically charged or a part of the chip gets stuck inside the apparatus, the detector erroneously detects it even though the top of the piled chips has not reached the predetermined height yet.